ES2696206T3 - Spray drying apparatus for dehydrated filtering and air pollution control system - Google Patents

Abstract

A spray drying apparatus (50; 50A; 50B; 50C), including: a spray nozzle (54) for spraying the filtrate (33) supplied from a dehydrator (32) via a filtrate feed line (L21) to a spray drying apparatus body; an introduction port (52) provided in the body of the spray drying apparatus, for introducing combustion gases (18) to dry the filtrate (33) sprayed from the spray nozzle (54); a drying region (L) formed in the body of the spray drying apparatus, for drying the sprayed filtrate (33) with the combustion gases (18); a discharge port (53) to discharge the combustion gases (18); a washing nozzle (60) to launch a washing liquid fed by a washing liquid supply line (L22) in order to wash the spray nozzle (54) and the interior of the body of the apparatus, the line of washing liquid supply (L22) from the filtering supply line (L21); a compressor (58) to introduce compressed air (59) to the spray nozzle (54) through an air supply line (L23) to facilitate spraying and to the washing nozzle (60) through the line (L24) excluding the washing period; and a detection unit for detecting spray failure at the spray nozzle (54) or drying failure; and a determination unit (85) for determining whether the spray and drying states of the filtrate (33) are good or bad based on the detection result of the detection unit; where a control unit (86) indicates and commands the flushing of the spray nozzle (54) and the interior of the body of the apparatus by the flushing nozzle (60) when it is determined that there is spray and drying failure as a result of the determination made by the determination unit (85).

Description

DESCRIPTION

Spray drying apparatus for dehydrated filtering and air pollution control system Field

The present invention relates to a spray drying apparatus for dehydrated filtering generated in the treatment of flue gases for treating combustion gases discharged from a boiler, and an air pollution control system.

Background

An air pollution control system is conventionally known for treating combustion gases discharged from a boiler installed in a thermal power plant, or the like. Such air pollution control system includes: a denitrifier to remove nitrogen oxides from the combustion gases of the boiler; an air heater to recover heat from the combustion gases passing through the denitrifier; a precipitator to remove ash dust from the combustion gases after heat recovery; and a desulfurizer for removing sulfur oxides from combustion gases from which dust has been removed. A typical desulfurizer used is a wet type desulfurizer that removes sulfur oxides from combustion gases by making gas-liquid contact between limestone absorbent, for example, and the combustion gases.

The effluent discharged from the wet type desulphurizer (hereinafter referred to as "absorption suspension") contains a large number of various types of toxic substances including ions, such as chlorine ions or ammonium ions, and mercury. Thus, these toxic substances must be removed from the desulfurized effluent before said desulfurized effluent is discharged to the outside of the system. However, the treatment to remove many types of toxic substances contained in the desulfurized effluent is a complicated process and, therefore, the cost of its treatment is high. In view of this, a method has been proposed for treating desulfurized effluent within a system without disulfurizing effluent discharge to the outside of the system to save the treatment cost of the desulfurized effluent. For example, patent documents 1 to 3 describe an air pollution control apparatus in which a plant for spraying and gasifying desulphurized effluent is installed separately so as to be branched from a main line combustion gas line to the that a denitrifier, an air heater, a precipitator and a desulphurizer are connected, part of the combustion gases is introduced to this installation from the main line combustion gas line, the desulphurized effluent is pulverized and evaporated in the exhaust gases. combustion in the facility to precipitate toxic substances, and then the gas is returned to the main line flue gas line (patent documents 1 to 3).

Appointment list

Patent document

Patent Document 1: Japanese Patent Application published number Sho. 63-200818

Patent Document 2: Japanese Patent Application published number Hei. 9-313881

Patent Document 3: US 2012/0240761

Summary

Technical problem

Although, in the air pollution control apparatus of patent documents 1 to 3, the installation for bifurcating part of combustion gases from the flue gas duct and spraying and gasifying desulfurized effluent (or sump solution) of the desulphurizer is disposed to evaporate the desulfurized effluent, the desulphurized effluent of the desulphurizer contains a solid component, thus giving rise to the problem that satisfactory spray drying is avoided.

In addition, in recent years, in installations for the control of air pollution, zero drainage has been necessary due to compliance with the regulations on effluents. Thus, the arrival of a stable operation air pollution control facility that achieves zero drainage has been very necessary.

A spray dryer for drying desulphurized effluent can be used as said facility that does not perform drainage. However, when the desulfurized effluent is spray dried with combustion gases from a boiler, the following problems arise.

The combustion gases of the boiler contain ash in high concentration. Additionally, when the desulfurized effluent is evaporated, a large amount of precipitated salt contained in the effluent is generated, possibly resulting in the deposition or generation of scale within the spray dryer.

The interior of the appliance can be washed during the operation of the boiler by dividing an inlet and an outlet of the appliance with regulators or the like. In terms of safety, however, it is difficult for an operator to enter directly into the spray dryer and perform a washing operation. You also have to finish the wash in a short period of time.

In view of the above problems, an object of the present invention is to provide a spray drying apparatus for dehydrated filtration and an air pollution control system capable of achieving zero drainage of desulfurized effluent from a desulphurizer.

Problem solution

According to a first aspect of the present invention for the purpose of solving said problems, a spray drying apparatus for dehydrated filtering according to claim 1 is provided.

According to another aspect of the present invention, the spray drying apparatus for dehydrated filtration is provided, wherein the detection unit is any of, or a combination of, a differential pressure manometer, a gas thermometer, a humidity meter gas, and a thermometer on a surface of the body of the apparatus.

According to another aspect of the present invention, the spray drying apparatus for dehydrated filtration is provided including: a cooling unit for cooling the interior of the body of the appliance heated by the combustion gases air stream.

According to another aspect of the present invention, the spray drying apparatus for dehydrated filtering is provided, wherein the discharge orifice is inclined towards an upper side of the spray drying apparatus body with respect to a horizontal direction.

According to another aspect of the present invention, the spray drying apparatus for dehydrated filtration is provided, wherein the wash liquid is any of, or a combination of, the dehydrated filtrate, water and steam. According to another aspect of the present invention, the spray drying apparatus for dehydrated filtering is provided, including: a washing liquid discharge line for discharging washing effluent from the washing unit.

According to another aspect of the present invention, an air pollution control system according to claim is provided.

Advantageous effects of the invention

According to the present invention, the washing unit is provided for washing the interior of the spray drying apparatus. If spraying fails, the combustion gas supply to the spray drying apparatus is interrupted and then the spray nozzle and the inside of the body of the appliance can be washed without an operator entering the interior of the appliance body .

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic configuration diagram of an air pollution control system according to a first embodiment.

Figure 2 is a schematic view illustrating a spray drying apparatus for dehydrated filtration according to the first embodiment.

Figure 3 is a cross-sectional view illustrating a main part of the spray drying apparatus for dehydrated filtration.

Figure 4 is a schematic view illustrating a treatment tank in which untreated washing effluent and combustion gases are introduced.

Figure 5 is a schematic view illustrating the spray drying apparatus provided with a detection unit.

Figure 6 is a schematic view illustrating a spray drying apparatus for dehydrated filtration according to a second embodiment.

Figure 7 is a schematic view illustrating a spray drying apparatus for dehydrated filtration according to a third embodiment.

Description of realizations

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

First realization

Figure 1 is a schematic configuration diagram of an air pollution control system according to the first embodiment. An air pollution control system 10 illustrated in Figure 1 is an apparatus for removing toxic substances, such as nitrogen oxides (NOx), sulfur oxides (SOx) and mercury (Hg), from combustion gases 18 of a boiler 11, such as a coal combustion boiler that uses coal as fuel, or a fuel oil combustion boiler that uses heavy oil as fuel, for example.

The air pollution control system 10 includes: the boiler 11 for burning a fuel F; a denitrifier 12 for removing nitrogen oxides present in the combustion gases 18 of the boiler 11; an air heater 13 for recovering heat from the denitrified combustion gases 18; a precipitator 14 for removing ash dust in the heat-recovered combustion gases 18 as precipitated ash 16; a desulphurizer 15 for removing sulfur oxides contained in the dustless combustion gases 18 with limestone suspension 20, which is an absorbent; a dehydrator 32 for recovering plaster 31 from the absorption suspension 30 discharged from the desulphurizer 15; a spray drying apparatus 50 (spray drying apparatuses 50A to 50C to be described below) including spray means for spraying dehydrated filtrate 33 from dehydrator 32; and a line of introduction of flue gases L ¹¹ to introduce part of the combustion gases 18 to the spray drying apparatus 50. This allows the dehydrated filtrate 33, from which the gypsum 31 has been recovered, to be spray dried in the spray drying apparatus 50 with the introduced combustion gases 18. Thus, a zero drainage of desulfurized effluent can be achieved with stability. The denitrifier 12 is an apparatus for removing nitrogen oxides present in the combustion gases 18 fed from the boiler 11 via a gas supply line L ¹ and has a denitrification catalyst layer (not shown). A reducing agent injector (not shown) is disposed upwardly of the denitrification catalyst layer and a reducing agent is injected into the combustion gases 18 from the reducing agent injector. Examples of the reducing agent may include ammonia, urea and ammonium chloride. The nitrogen oxides in the combustion gases 18 introduced into the denitrifier 12 are brought into contact with the denitrification catalyst layer, so that the oxides of nitrogen in the combustion gases 18 decompose into nitrogen gas (N ² ) and water (H ² O) and removed. The mercury present in the combustion gases 18 has a higher proportion of divalent water-soluble mercury chloride when the chlorine (Cl) content increases, thereby allowing the mercury to be more readily collected in the desulphurizer 15 to be described later.

Note that the anterior denitrifier 12 is not an essential component. If the concentration of nitrogen oxides and the concentration of mercury in the combustion gases 18 of the boiler 11 are extremely low or if these substances are not found in the combustion gases 18, the denitrifier 12 can be omitted.

The air heater 13 is a heat exchanger for recovering heat from the combustion gases 18 fed by a flue gas supply line L ² after removing the nitrogen oxides therefrom in the denitrifier 12. The temperature of the gases of combustion 18, which have passed through the denitrifier 12, is from the range of about 300 ° C to 400 ° C, which is high. Thus, the air heater 13 performs heat exchange between the combustion gases at high temperature 18 and combustion air at room temperature. The combustion air that now has a high temperature by the heat exchange is fed to the boiler 11. On the other hand, the combustion gases 18 that have undergone thermal exchange with the combustion air at room temperature are cooled to approximately 150 ° C .

The precipitator 14 serves to remove ash dust present in the combustion gases 18 fed by a gas feed line L ³ after heat recovery. Examples of the precipitator 14 may include an inertial precipitator, a centrifugal precipitator, a filter type precipitator, an electronic precipitator, and a wash precipitator, although the precipitator 14 is not limited to any particular precipitator.

The desulfurizer 15 is an apparatus for performing wet-type extraction of sulfur oxides in the combustion gases 18 fed by a gas feed line L ⁴ after the extraction of ash dust. In this desulphurizer 15, limestone suspension 20 (aqueous solution obtained by dissolving limestone powder in water) is used as an alkaline absorbent. The temperature inside the device is controlled so that it is approximately 30 to 80 ° C. The limestone suspension 20 is fed from a limestone suspension feeder 21 to a lower portion 22 of the desulfurizer 15. The limestone suspension 20 fed to the lower portion 22 of the desulphurizer 15 is sent to a plurality of nozzles 23 in the desulphurizer 15 by a line of absorbent supply (not shown) and released from the nozzles 23 to an upper portion 24. The gas-liquid contact is made between the combustion gases 18 that rise from the lower portion 22 of the desulphurizer 15 and the limestone suspension 20 released from the nozzles 23, causing the sulfur oxides and the mercury chloride present in the combustion gases 18 to be absorbed by the limestone suspension 20 and thus be separated and removed from the combustion gases 18. The combustion gases 18 purified by the limestone suspension 20 is discharged from the upper portion 24 of the desulphurizer 15 as purified gas 26 and discharged to the exterior of the system through a chimney 27.

Within the desulphurizer 15, the sulfur oxides, SOx, present in the combustion gases 18 and the limestone suspension 20 produce a reaction represented by the following formula (1).

In addition, the limestone suspension 20, which has absorbed SOx present in the combustion gases 18, is oxidized by air (not shown) fed to the lower portion 22 of the desulphurizer 15 producing a reaction represented by the following formula (2) with air.

In this way, SOx present in the combustion gases 18 is captured in the form of gypsum, CaSO4-2H2O, in the desulphurizer 15.

As the liquid held in the bottom portion 22 of desulfurizer 15 is pumped and used as limestone suspension 20 as described above, gypsum, CaSO ^4-2 H ² O, mixed with limestone slurry pumped 20 along with the operation of the desulphurizer 15 according to the reaction formulas (1) and (2). Next, the suspension of pumped limestone-gypsum (limestone suspension with which gypsum has been mixed) is called absorbent. The absorption suspension (limestone-gypsum suspension) used for the desulfurization is discharged to the outside by the lower portion 22 of the desulphurizer 15, sent to the dehydrator 32 by an absorber line L ²⁰ , and dehydrated in the dehydrator 32. In addition to gypsum, the absorption suspension 30 contains heavy metals, such as mercury and halogen ions such as Cl ", Br", I "or F".

The dehydrator 32 serves to separate the absorption suspension 30 into a solid component including the gypsum 31 and the dehydrated filtrate 33, which is a liquid component. Examples of the dehydrator 32 may include a belt filter, a centrifuge, and a centrifugal settler of the decanter type. The plaster 31 is separated from the absorption suspension 30 discharged from the desulfurizer 15 by the dehydrator 32. Then, the mercury chloride in the absorption suspension 30 is separated from the liquid together with the plaster 31 while being adsorbed to the plaster 31. The separated plaster 31 is discharged to the exterior of the system (hereinafter referred to as "the exterior of the system").

On the other hand, the dehydrated filtrate 33, which is the separated liquid, is sent to the spray drying apparatus 50 by a dehydrated filtrate feed line L ²¹ . Note that the dehydrated filtrate 33 can be temporarily retained in a filter tank (not shown).

The spray drying apparatus 50 includes: means for introducing gases to introduce part of the combustion gases 18 through the bifurcated combustion gas introduction line L ¹¹ of the combustion gas supply line L ² , which is a main line for the combustion gases 18 coming from the boiler 11; and spray means for spraying or spraying the dehydrated filtrate 33. The dehydrated filtrate sprayed or sprayed 33 is dried by evaporation by means of the heat of the introduced combustion gases 18. Note that the sign L ¹² denotes a line of supply of combustion gases to return to the gas supply line L ³ the combustion gases 18 contributing to the drying in the spray drying apparatus 50.

According to the present invention, the dehydrated filtrate 33 obtained by recovering the gypsum 31 from the absorption suspension 30 is spray dried. Thus, obstruction in the spray means can be prevented.

More specifically, since the actual absorption suspension 30 is not sprayed, the amount of dried particles generated together with the evaporation of the desulfurized effluent can be significantly reduced. As a result, the blockage produced by the adhesion of the dried particles can be reduced. In addition, mercury chloride is also separated and removed together with gypsum 31 by dehydration of the absorption suspension 30. Thus, the concentration of mercury in the combustion gases 18 is prevented from increasing during the spraying of the effluent.

In addition, part of the combustion gases 18 flowing into the air heater 13 are branched from the combustion gas supply line L ² via the combustion gas introduction line L ¹¹ according to the present embodiment. Thus, the temperature of the combustion gases is high (from 350 to 400 ° C) and therefore the spray drying of the dehydrated filtrate 33 can be carried out efficiently.

Note that the dehydrated filtrate 33 is sprayed to the body of the apparatus by compressed air 59 fed from a compressor 58 at a predetermined flow rate and with a particle size of the spray droplets.

Figure 2 is a schematic view illustrating the spray drying apparatus for dehydrated filtration according to the present embodiment. Figure 3 is a cross-sectional view illustrating a main part of the spray drying apparatus for dehydrated filtration.

As shown in Figure 2, the spray drying apparatus 50A of the present embodiment includes: a gas introduction port 52 disposed in a portion of a side wall 51b near an upper part (lid) 51a of the apparatus body spray drying, for introducing the combustion gases 18 to dry by liquid spray 33a of the dehydrated filtrate 33; a spray nozzle 54 hanging from the top (lid) 51a of the spray drying apparatus body, for spraying the dehydrated filtrate 33; a spray drying region L formed in the spray drying apparatus body, for use in drying the spray dried filtrate 33 with the combustion gases 18; a gas discharge orifice 53 disposed in a portion of the side surface 51b near the bottom of the spray drying apparatus body, for discharging the combustion gases 18 contributing to the spray drying towards the gas supply line L ³ , which is a main conduit of combustion gases; and a washing nozzle 60, which is a washing unit for washing the spray nozzle 54 and the interior of the body of the apparatus with washing liquid.

Here, eight wash nozzles 60 are disposed in the present embodiment along the interior surface of the side wall 51b of the body of the apparatus as shown in Figure 3.

Here, for the introduction of the combustion gases 18, the combustion gases 18 can be introduced into the spray drying apparatus 50A by means of a difference in the pressure loss between the L ² flue gas supply line and the line of introduction of combustion gases L ¹¹ or combustion gases 18 can be introduced with an induced draft fan, or the like, when necessary.

The dehydrated filtrate 33 is released as the spray liquid 33a to the combustion gases 18 having a laminar flow from the spray nozzle 54.

Here, the spray nozzle 54 is not limited to any particular type provided that it can spray the dehydrated filtrate 33 with a predetermined droplet diameter. For example, spray media such as a two fluid nozzle or a rotary atomizer may be used. Note that the two fluid nozzle is suitable for spraying a relatively small amount of dehydrated filtrate 33 and the rotary atomizer is suitable for spraying a relatively large amount of dehydrated filtrate 33.

In addition, the number of such nozzles is not limited to one. Multiple nozzles can be arranged according to the treatment amount.

In the present invention, to facilitate spraying, the compressor 58 is used to introduce the compressed air 59 to the nozzle 54 via an air supply line L ²³ . Here, the compressed air 59 and the dehydrated filtrate 33 are introduced separately to the spray nozzle 54 and sprayed as the spray liquid 33a into the body. Note that the sign V ⁵ denotes a switching valve for switching the introduction of air.

To facilitate the successful drying of the spray liquid 33a sprayed from the spray nozzle 54, the length of the spray drying region L within the column of the spray drying apparatus 50A is changed according to the rate of evaporation of the filtrate with the In order to prolong the residence time of the spray liquid 33a because the filtrate is desulfurized filtrate having a boiling point higher than that of ordinary water.

Here, the combustion gases 18 that contribute to spray drying are discharged by the gas discharge orifice 53 disposed in the portion of the side wall 51b near the bottom of the spray drying apparatus 50A.

When sprayed by the spray nozzle 54, the dehydrated filtrate 33 comes in contact with the combustion gases 18 introduced in the spray drying region L, whereby they are spray dried.

By drying the dewatered filtrate 33 in this manner, zero drainage of the dehydrated filtrate 33 of the desulphurizer 15 can be achieved.

Since the dehydrated filtrate 33 contains various types of salts, its spray-dried solid 56 is discharged from a discharge hopper 51c disposed in the lower part of the spray drying apparatus body through a continuous discharge line L ³¹ .

The washing nozzle 60 disposed in an upper portion within the body of the apparatus performs purge of air excluding the washing period in order to avoid blocking due to the influence of the spray-dried solid 56, or the like.

For purging air, air 59 from compressor 58 is flowed through a line L ²⁴ . Note that a switching valve V6 for switching the introduction of air is interposed in line L ²⁴ .

When the interior of the body of the apparatus is washed with the washing nozzle 60, the washing is done by stopping the introduction of air and feeding the dehydrated filtrate 33.

Thus, when the washing is carried out, the dehydrated filtrate 33 is fed to the washing nozzle 60 by a line of washing liquid L ²² bifurcated from the dehydrated filtrate feed line L ²¹ . Note that the signs V ³ and V ⁴ indicate switching valves for switching the supply of dehydrated filtrate 33.

The washing liquid 61, which is the dehydrated filtrate 33 sprayed from the washing nozzle 60, washes the inner wall surface of the body of the apparatus, the gas discharge orifice 53, the spray nozzle 54, and the inner surface of the the hopper 51c in the lower part of the body of the apparatus, and wash out foreign substances such as the adhered spray dried solid 56, in order to restore the above portions to a clean state.

Figure 4 is a schematic view illustrating a treatment tank in which untreated washing effluent and combustion gases are introduced.

As shown in FIG. 4, the washing effluent 62 used for the washing is discharged from one end of the hopper 51c in the lower part of the body of the apparatus and introduced to an effluent treatment tank 73 by means of a discharge line. washing liquid L ³² .

Since the spray dried solid 56 generated during the drying is discharged through the continuous discharge line L ³¹ , the switching valves V ¹ and V ² are switched so that no washing effluent 62 flows to the continuous line of download L ³¹ .

Note that the wash effluent 62 can be treated in an effluent treatment facility inside or outside the system after being retained in the effluent treatment tank 73.

Alternatively, the wash effluent 62 may be introduced to the absorbent in the lower portion 22 of the desulfurizer 15. Alternatively, the wash effluent 62 may be introduced to the dehydrator 32 to dehydrate the absorption suspension 30 of the desulphurizer 15.

As shown in Figure 5, the presence or absence of spray and drying failure due, for example, to the generation of scale within the spray drying apparatus is detected by a detection unit, such as several sensors.

Any one, or a combination, of a differential pressure manometer 81, a gas thermometer 82, a gas moisture meter 83, a thermometer 84 on the surface of the body of the apparatus, etc., can be used as the detection unit for detecting such a failure, although the present invention is not limited thereto.

Figure 5 is a schematic view illustrating an example of the spray drying apparatus provided with several sensors.

As shown in FIG. 5, pressure gauges have been arranged in the flue gas introduction line L ¹¹ and the flue gas supply line L ¹² to measure the pressure difference between the inlet and the outlet to introduce and discharging gas in the spray drying apparatus 50A. The pressure difference in the combustion gases 18 is then detected by the differential pressure gauge 81.

A determination unit 85 determines, for example, whether the pressure difference has increased or not above a predetermined pressure.

In addition, the gas thermometer 82 is arranged in the flue gas supply line L ¹² to measure the exit temperature of the combustion gases 18 discharged from the spray drying apparatus 50A. In this way, the temperature of the combustion gases 18 on the outlet side is detected by the gas thermometer 82.

If the temperature of the gases has increased or not above a predetermined temperature, then the determination unit 85 determines it. When the temperature of the combustion gases introduced is 350 ° C and the spray drying has been carried out correctly, example, the discharge temperature of the combustion gases on the outlet side has decreased only 170 ° C. When the discharge temperature is ^{2 0 0} ° C, for example, it can be determined that there is a failure in spray drying.

In addition, the humidity meter 83 for measuring the concentration of moisture in the exhaust gases, which are the combustion gases 18 discharged from the spray drying apparatus 50A, is arranged in the flue gas supply line L ¹² . In this way, the humidity of the combustion gases 18 is detected by the humidity meter 83.

If the humidity concentration has decreased or not below a predetermined concentration, then the determination unit 85 determines it. When the spray drying has been carried out correctly, the humidity in the combustion gases is 20% by volume. However, when the moisture in the combustion gases is 17 or 18% by volume, for example, it can be determined that there is failure in spray drying since droplets can not be evaporated.

Alternatively, such failure can be detected from an anomaly in the outer surface temperature of the body of spray drying apparatus or the like. Accordingly, temperature sensors (eg, thermocouples or the like) 84a, 84b, and 84c are mounted at predetermined positions on the outer surface of the side wall 51b of the body of the apparatus, so that the surface temperature is detected by the thermometer 84. on the surface of the body of the device. If the temperature has decreased or not below a predetermined temperature due to the adhesion of the spray-dried material to the inner surface, for example, it is determined by the determination unit 85.

Leaving the thermocouples aside, the temperature sensing can be performed with a non-contacting sensor, or a combination of a contact type sensor and a contactless type temperature sensor can be used. The present embodiment includes: the various sensors 81 to 84 for detecting spray failure in the spray nozzle 54 or drying failure; the determining unit 85 for determining whether the spray and drying states of the dehydrated filtrate 33 are good or bad based on the results of sensor detection; and a control unit ⁸⁶ for indicating or ordering the washing of the spray nozzle 54 and the interior of the body of the apparatus by the washing nozzle 60 when it is determined that there is spray and drying failure as a result of the determination made by the unit of determination 85.

Furthermore, as shown in FIG. 1, regulators 70, 70 have been arranged in the line of introduction of flue gases L ¹¹ and the line of supply of flue gases L ¹² in the air pollution control system ¹⁰ with in order to stop the entry of the combustion gases 18 when it is determined that there is failure in the spray drying.

In addition, after stopping the introduction of the combustion gases 18, a cooling unit 71 introduces refrigerant gas 72 to the body of the apparatus in order to cool the interior of the body of the appliance heated by the air stream of the combustion gases. in preparation for washing. The interior of the body of the apparatus is thereby cooled to a predetermined temperature (for example, 40 to 50 degrees) or lower.

For example, an air cooling fan, a two fluid nozzle compressor, general service air, or the like, such as the refrigeration unit 71 can be used. Furthermore, after the interior of the body of the apparatus has been cooled to the predetermined temperature, the cooling of the interior can be facilitated by releasing the dehydrated filtrate 33 from the washing nozzle 60 and the spray nozzle 54.

When the introduction of the combustion gases 18 is stopped, the untreated gas 18a remaining in the body of the apparatus is sent to the effluent treatment tank 73 via the washing liquid discharge line L ³² . Then, the gas 18a is bubbled, and treated with the wash effluent 62.

Furthermore, during the rapid cooling performed by the cooling unit 71 or the washing liquid, for example, gas having a volume greater than or equal to the internal capacity of the body of the apparatus is generated within the body of the apparatus. The untreated gas 18a is sent to the effluent treatment tank 73 and is treated therein without being able to escape to the outside of the system.

Next, a method which is carried out after determining that there is a failure in spray drying during the operation of the spray drying apparatus will be described.

1) Step 1

Typically, spray drying is performed by introducing the dehydrated filtrate 33 and the combustion gases 18 into the spray drying apparatus 50. Then, the regulator 70 is opening. Air purging is also performed during such spray drying by feeding air 59 to the washing nozzle 60.

2) Step 2

The failure in spray drying is determined by the determination unit 85 based on the detection carried out by several sensors.

The control unit 86 suggests or orders a stop operation according to the results of the determination unit 85, thus stopping the feeding of the dehydrated filtrate 33 to the spray nozzle 54.

3) Step 3

The regulator 70 is switched in order to stop the entrance of the combustion gases 18 to the spray drying apparatus.

4) Step 4

The valve V ¹ in the continuous discharge line L ³¹ is closed to stop the discharge of the spray-dried solid 56, while the valve V ² in the washing liquid discharge line L ³² is opened to prepare the discharge of the effluent of washing 62.

In addition, the untreated gas 18a, resulting from the stoppage of the combustion gas inlet 18, is introduced to the effluent treatment tank 73 through the washing liquid discharge line L ³² and is treated. 5) Step 5

The cooling gas 72 is fed to the body of the apparatus by the cooling unit 71 and the interior is cooled to the predetermined temperature.

6) Step 6

The dehydrated filtrate 33 is ejected from the washing nozzle 60 to wash the spray nozzle 54 and the interior of the apparatus.

7) Step 7

The washing effluent 62 is discharged to the effluent treatment tank 73 through the washing liquid discharge line L ³² . The effluent is treated in the effluent treatment facility within the system or returned to the absorber or dehydrator.

8) Step 8

Once a predetermined washing operation has been performed for a predetermined period of time, the end of the washing is determined.

Additionally, an operator or the like can enter the interior of the body of the apparatus through a manhole to check the interior when necessary.

9) Step 9

A recovery operation is performed.

Several lines are switched.

The gas regulator 70 is opened to initiate the introduction of the combustion gases 18.

Then, once a predetermined temperature has been reached, the dehydrated filtrate 33 is fed to initiate spray drying.

The spray drying apparatus for dehydrated filtration according to the present embodiment allows the washing maintenance to be performed in a short period of time by remote control without requiring an operator to enter the interior of the body of the apparatus.

In addition, no washing liquid is discharged to the outside of the system. In addition, the untreated gas that remains after the spray drying stop is treated, thus preventing it from being discharged to the outside.

If the spray drying has been carried out correctly or is not determined with several sensors, it is possible to perform the washing maintenance in a short period of time by remote control.

In addition, the interior of the apparatus is cooled by the cooling unit after the stop of the spray drying, thus being able to immediately carry out the washing carried out by the washing unit.

Second embodiment

Figure 6 is a schematic view illustrating a spray drying apparatus for dehydrated filtration according to the second embodiment. Note that the components identical to those of the spray drying apparatus 50A according to the first embodiment will be indicated by the same reference numerals and their description will be omitted.

As shown in Figure 6, the spray drying apparatus 50B of the present embodiment is configured in such a way that the discharge orifice 53 of the combustion gases 18, disposed in a lower portion of the body of the apparatus, is inclined towards an upper side of the spray drying apparatus body with respect to the horizontal direction at a predetermined angle (to degrees).

This prevents the dehydrated filtrate 33, which is the washing liquid dropped from the washing nozzle 60, and the washing effluent ^{6 2} from entering the flue gas supply line L ¹² connected to the gas supply line L3. , which is the flue gas duct.

Third realization

Figure 7 is a schematic view illustrating a spray drying apparatus for dehydrated filtration according to the third embodiment. Note that the components identical to those of the spray drying apparatus 50A according to the first embodiment will be indicated by the same reference numerals and their description will be omitted.

As shown in Figure 7, the spray drying apparatus 50C of the present embodiment is configured in such a way that the washing liquid to be fed to the washing nozzle 60 is not limited to the dehydrated filtrate 33, and some or several of the dehydrated filtrate 33, water (industrial water) 74 and steam 75. When these are used in combination, the commutation can be effected with the switching valves V7 and V8 ad libitum.

Thus, a type of washing liquid can be selected according to several cases, for example, where the effluent can be discharged or not or where the scale can be easily removed or not.

List of reference signs

10: air pollution control system

11: boiler

12: denitrifier

13: air heater

14: precipitator

15: desulphurizer

16: precipitated ash

18: combustion gases

30: absorption suspension

: dehydrator

: dehydrated filtrate

, 50A to 50C: spray drying apparatus: gas introduction hole

: gas discharge orifice

: spray nozzle

: air

: washing unit (washing nozzle)

: washing effluent

: regulator

: refrigeration unit

Claims (7)

1. A spray drying apparatus (50; 50A; 50B; 50C), including: a spray nozzle (54) for spraying the filtrate (33) supplied from a dehydrator (32) via a filtrate feed line (L ²¹ ) to a spray drying apparatus body; an introduction hole (52) disposed in the spray drying apparatus body, for introducing combustion gases (18) to dry the spray filtrate (33) from the spray nozzle (54); a drying region (L) formed in the spray drying apparatus body, for drying the spray filtrate (33) with the combustion gases (18); a discharge orifice (53) for discharging the combustion gases (18); a washing nozzle (60) for throwing a washing liquid fed by a washing liquid feed line (L ²² ) in order to wash the spray nozzle (54) and the interior of the body of the apparatus, bifurcating the line of washing liquid feed (L ²² ) of the filtrate feed line (L ²¹ ); a compressor (58) for introducing compressed air (59) to the spray nozzle (54) by means of an air feed line (L ²³ ) to facilitate spraying and the washing nozzle (60) via the line (L ²⁴ ) excluding the washing period; Y a detection unit for detecting spray failure in the spray nozzle (54) or drying failure; and a determining unit (85) for determining whether the spraying and drying states of the filtrate (33) are good or bad based on the result of detection of the detection unit; where a control unit (86) which indicates and orders the washing of the spray nozzle (54) and the interior of the body of the apparatus through the washing nozzle (60) when it is determined that there is spray failure and drying as a result of the determination made by the determination unit (85). 2. The spray drying apparatus (50; 50A; 50B; 50C) according to claim 1, wherein the detection unit is one or a combination of a differential pressure gauge (81), a gas thermometer (82), a gas moisture meter (83), and a thermometer (84) on a surface of the body of the apparatus . 3. The spray drying apparatus (50; 50A; 50B; 50C) according to claim 1, including: a cooling unit (71) for cooling the interior of the body of the appliance heated by the combustion gases (18). 4. The spray drying apparatus (50; 50A; 50B; 50C) according to any of claims 1 to 3, wherein the discharge orifice (53) is disposed in a lower portion of the spray drying and inclined apparatus body. to an upper side of the spray-drying apparatus body with respect to a horizontal direction. 5. The spray drying apparatus (50; 50A; 50B; 50C) according to any of claims 1 to 4, wherein the wash liquid is any of, or a combination of, the filtrate (33), water and steam. 6. The spray drying apparatus (50; 50A; 50B; 50C) according to any of claims 1 to 5, including: a washing liquid discharge line (L ³² ) to discharge washing effluent. 7. An air pollution control system including: a boiler (11) to burn a fuel (F); an air heater (13) for recovering heat from combustion gases (18) discharged from the boiler (11) through a flue gas duct; a precipitator (14) for removing ash dust in the combustion gases (18) after heat recovery; a desulfurizer (15) for removing sulfur oxides contained in the combustion gases without dust (18) with an absorbent; a dehydrator (32) for recovering absorption suspension gypsum discharged from the desulfurizer (15); the spray drying apparatus (50; 50A; 50B; 50C;) according to any of claims 1 to 6 for spraying filtrate (33) from the dehydrator (32); a line of introduction of flue gases (L ¹¹ ) branched from the flue gas duct to introduce part of the combustion gases (18) to the spray drying apparatus (50; 50A; 50B; 50C); a line of supply of combustion gases (L ¹² ) to return the combustion gases to the flue gas duct; Y a regulating unit interposed in the line of introduction of combustion gases (L ¹¹ ) and the line of supply of combustion gases (L ¹² ) to stop the introduction and restart the return of the combustion gases (18), respectively.